Paper products and manufacture thereof



United States Patent PAPER PRODUCTS AND MANUFACTURE THEREOF John P. Bainbridge, Jr., Marblehead, and Edward S. Blake, Lynnfield, Mass, assi'gnors to Monsanto Chemical Company, St. Louis, Mm, a corporation of Delaware N0 Drawing. Application December 22, 1952,. Serial No. 327,448

19 Claims. (Cl. 117-154) The present invention relates to'paper articles and paper manufacture-and it more particularly relatestothe productionof soft paperp roducts, especially paper products of the facial tissue or other tissue type whicharesoft to the touch.

In preparing paper products suitable for use as-paper toweling or facial tissue two methods of arriving ata product having satisfactory surface softness have been employed. In one of these methods the pulp used-impreparing the tissue is beaten tov such a slight degree that the paperformed therefrom has the requisite surfacesoftness. Such products, however, have the disadvantage of being exceptionally weak andjdisintegrate readily totheannoyance of the user. In the other method the pulp used in preparing the tissue is beaten to such a degree that the paper formed therefrom will have :a re'latively'satisfactory strength and will not disintegrate readilywhen used. However, such products per se are not sufficiently soft to the touch to b'e'received favorably. In order to render such products commercially acceptable from the standpoint of surface softness, it is necessary to treat them with an agent which will give the requisite softness without introducing other objectionable features. Many chemical agents of the hygroscopic and waxy or wetting agent type have been tried for this purpose. A few have been successful to a limited extent but they donot give the optimum surface softness desired. Many :agents have been tried unsuccessfully and these have beenunsuccessful for various reasons. One primary reason for failure is that they donot impart the requisite surface softness to paper. Some-agents accomplish this in some degree but they introduce complicating factors such as bad odor,- poor aging properties, toxic effects, decreased water absorbency, etc. For example, glycerine which is a hygroscopic'agent, gives a softening effect but has the disadvantage of lowering the tensilestrength andthe water absorbency" of the tissue, and it also imparts an objectionable damp feel'to the tissue. As another example, sodium oleate, which isa wetting agent, has the disadvantages of; poor aging characteristics and insufficient softening action. Many other examples of specific agents which have been found to be unsuitable could be cited but it is believed'the remarks made with respect to the agents specifically mentioned indicate that the suitability of any particular agent for the surface softening of paper facial tissue cannot: be predicted;

It is one object'of' this invention to provide methods for softening the surface of paper products.

It is a further object of. this invention to provide paper products which are softer to the touch than the, paper per se. 7

It is a further object of this, inventionto provide, paper .suitablefor useas-ffacialtissue andhaving the requisite surface softness and utilityfor such purpose.

Still further objects and advantages of this invention will become apparent. from the following. description andithe appended claims.

[Ce Eatented Jan. 22, 1957 The objects of this invention are attained, in general, by providinga papenproduct, preferably paper facial tissue, containinga water soluble. aliphatic disulfonic acid containing at least, 10 carbon atoms, or water: soluble derivatives thereofinanarnount sufiicient to soften, the paper product but insufficient to impair thev utility ofsuch paper product,

The aliphatic disulfonic acid containing. at. least 10 carbon atoms or water soluble derivatives thereof, hereinafter referred to as theagent for convenience in description, maybe. appliedjdirectly to the, paper after itis formed or itmay .be incorporated into. the paper product prior to the manufacture of such producton. the. paper machine. The first of these'procedures, is, preferred since it provides .apaperproduct,of higher tensile strength and 'does not interfere. with the manufacturing process for producing. the paper product. Aparticularlyl preferred method of application comprises spraying an aqueous solutionof'the agent on the surface-or surfaces of the paper product which it is d'esired to soften- Forexample, if the paper is in the form of a :sheet and it is only desired tosoften one surface of the. sheet, theagent need only be applied to that. surface. 7

The solution of'the zagent is mostsui tably applied by spraying; the solution on thepaper product since thisprocedure does not'appreciably affectthewet or dry tensile strength of the product. However, when the lowering, of the wet or dry tensile strength of the paper product is not undesirable, the; solutionof the agentmay be appliedto the paper product'in other ways, To, 0b tain .a;uniform softening effect, the agent shouldbe applied uniformly to the paper product. Inapplying, the ag ent tothe. paper produc y spraying, it is preferred to adjust the spray and the solids concentration ofthe agent in solution so as to obtainlittle or no surface wettingofthe paper-product. Under such conditions the agent-is' deposited primarilyon the surface of the paper product and appreciable penetration of the agent into the body of thepaperproduct is avoided, and no marked changeinthe, properties of the paper product, other than softening of. the surface to the touch, is noted.

The agent may also be incorporated in ,the, paper product by adding it to3a paper'furnish, that is, an-iaqueous slurry of paper pulp frorn'which thepaper sheet or product is-produced. However, this,proceduredoes not give as good-a result as the procedure of applying the agent to the paper product since the addition of. the agentto the furnish results in foamingand'other operating. difiiculties duringthe paper formingprocess and the strength of the product is less than,when. the agentis not addedto the furnish.

The agentrnay be appliedto iorincorporatedin any paper product where. softness or lack of harshnesstothe touch isv desirable or required, for, example, creped or uncrepfid sanitary tissues, facial tissues, toilet tissues, toweling and the like. Such productsare usually prepared from unsized to lightly sized pu-lps such asbleached or unbleached sulfite, sulfate, soda or groundwood pulps or mixturesofsuchjpulps. The present inventionzis particularly; directed to the softening of paper products which are-used 0n the -.huma-nskin and wheresoftness. to the touch, non-toxicity, non-irritationand satisfactory strength of theproduco are essential properties. The agents of thisin-yention aremost. suitably applied to such paper products as have a satisfactory strength for their intended use but do notper sehavethe requisite surface softness.

The amount of agent used--on or in the paper product may be varied considerably depending primarily on the particular agent used, the intended use of the paper product, and, thetype of pulp: from which the paper product is manufacturcd. However, normally theagent is used in small amounts, with some surface softening bemg obtained in most cases by the application of as little as 0.05% by weight of the agent, based on the dry weight of the paper product. However, in order to obtain a considerable surface softening eifect, it is preferable to apply at least 0.1% by weight of the agent, based on the dry paper product. Ordinarily, no advantages accrue in applying more than 2% by weight of the agent, based on the dry paper product, and it is preferred, in order to avoid alteration of the paper product properties, to apply not more than 1% by weight of the agent, based on the dry paper product. In general, therefore, the agent is applied to or incorporated in the paper products in amounts of about 0.05 to 2% by weight, and preferably between 0.1 and 1% by weight, based on the dry paper product.

The agents employed in this invention comprise the class of compounds which include the aliphatic disulphonic acids which consist of a normal or branched saturated carbon chain having'frorn to 30 carbon atoms to which are attached hydrogen atoms and two sulfonic acid groups (----SO3H groups), or halogenated derivatives thereof containing up to two halogen atoms, preferably chlorine atoms, attached to a carbon atom or atoms, or water-soluble salts of such compounds including the ammonium and alkali metal monoor di-salts. The alkali metal salts, particularly the di-sodium salts, are preferred over the acids per se or other water-soluble salts. The position occupied by the sulfonic acid groups or halogen, if such latter group is present, on the carbon chain is apparently not critical. As examples of compounds which may be employed may be mentioned dodecane disulfonic acids, dichloro dodecane disulfonic acids or the monoor di-sodium salts of such acids; cetane disulfonic acids or the monoor di-sodiurn salt thereof; octadecane disulfonic acids or mono-chlor octadecane disulfonic acids or the monoor di-sodium salts of such acids; eicosane disulfonic acids or the monoor di-sodium salt thereof; and the like. The preferred compounds from the standpoint of number of carbon atoms are those which contain from 16 to 22 carbon atoms.

The disulfonic acids employed in this invention and described above may be prepared by first reacting 1 mol of an alkane containing at least 10 carbon atoms, for example, from 10 to 30 carbon atoms, and preferably from 16 to 22 carbon atoms, with 2 mols of sulfur dioxide (S02) and 2 mols of chlorine (2 C12) in the presence of ultra-violet light at a temperature between about 35 and 80 C. until the alkane contains two sulfochloride (SOzCl) groups, after which the product is hydrolyzed with an alkanol to form the disulfonic acid and the corresponding chloride of the alcohol or is hydrolyzed with an alkali metal hydroxide to form the correspond ing disulfonic acid and alkali metal chloride. ter separation of the disulfonic acid and alkyl chloride as, for example, by distillation of the alkyl chloride from the product, the disulfonic acid may be employed as such or neutralized with a base capable of forming a Watersoluble monoor di-salt of such acid. Ammonium and alkali metal hydroxides or carbonates may be used for this purpose.

The agents employed in this invention are preferably soluble or dispersible in water to the extent of at least 25% by weight, and more particularly to the extent of about 25 to 60% by weight.

A further understanding of the processes and products of this invention will be obtained from the following specific examples which are intended to illustrate this invention but not to limit the scope thereof, parts and percentages being by weight.

Example I A 50% aqueous solution of the disodium salt of a dodecane disulfonic acid was sprayed uniformly on both sides of a creped, unsized paper facial tissue of double thickness in an amount sulficient to deposit 0. 5% of such salt on the tissue surface, based on the dry tissue weight. The tissue was then supercalendered. Whereas the original tissue, prior to treatment, had satisfactory strength and resistance to disintegration when Wet, such tissue was not sufiiciently soft to be commercially acceptable. The treated tissue, on the other hand, not only possessed the strength and resistance to disintegration of the original tissue, but was sufliciently soft to be commercially acceptable. Moreover, the treated tissue was non-toxic, was free of objectionable odor or color and did not acquire a bad odor or color over long periods of aging.

Example 11 A 50% aqueous solution of the disodium salt of an eicosane disulfonic acid was applied to both sides of a creped, unsized paper facial tissue of double thickness according to the procedure of Example I. The treated tissue was then supercalendered and was found to be softer than the treated tissue of Example I, but was otherwise equivalent in properties.

Similar results were obtained with the disodium salt of a mono-chlor eicosane disulfonic acid and with an eicosane disulfonic acid, with the exception that the latter compound rendered the tissue acidic.

Various changes and modifications may be made in the processes and paper products described herein, as will be apparent to those skilled in the art to which this invention appertains, without departing from the spirit and intent of this invention. Accordingly, it is to be understood that it isnot intended to limit this invention except by the scope of the appended claims.

What is claimed is:

l. A cellulosic fiber paper product comprising a substance selected from the class consisting of aliphatic disulfonic acids having at least 10 carbon atoms, halogencontaining aliphatic disulfonic acids having at least 10 carbon atoms and containing up to 2 halogen atoms which are attached to a carbon atom of said acid and watersoluble salts of said compounds, said substance being present in an amount sufiicient to soften the surface of said paper product.

2. A cellulosic fiber paper product comprising an aliphatic disulfonic acid having from 10 to 30 carbon atoms, said acid being present in an amount suflicient to soften the surface of said paper product.

3. A cellulosic fiber paper product as in claim 2, but further characterized in that said acid is present in amounts of about 0.05 to 2% by weight based on the dry paper product.

4. A cellulosic fiber paper product comprising a chlorinated aliphatic disulfonic acid having from 10 to 30 carbon atoms and up to two chlorine atoms which are attached to a carbon atom of said acid, said substance being present in an amount sufficient to soften the surface of said paper product.

5. A cellulosic fiber paper product comprising a watersoluble salt of a chlorinated aliphatic disulfonic acid having from 10 to 30 carbon atoms and up to two chlorine atoms which are attached to a carbon atom of said acid, said substance being present in an amount sufficient to soften the surface of said paper product.

6. A cellulosic fiber paper product comprising a watersoluble salt of an aliphatic disulfonic acid having from 10 to 30 carbon atoms, said salt being present in an amount suflicient to soften the surface of said paper product.

7. A cellulosic fiber paper product as in claim 6, but further characterized in that said salt is a sodium salt.

8. A cellulosic fiber paper product for use on human skin comprising a sodium salt of an aliphatic disulfonic acid having from 10 to 30 carbon atoms, said salt being present on the surface of said product which contacts the skin in an amount sufficient to soften said product to the touch.

wrap-1o 9. A cellulosic fiber paper product as in claim 8, but further characterized in that the paper product is selected from the class consisting of facial tissues, sanitary tissues, toilet tissues and paper toweling.

10. A cellulosic fiber paper product as in claim 9, but further characterized in that said salt is present in amounts of from about 0.1 to 1% by weight based on the dry paper product.

11. A cellulosic fiber paper product as in claim 8, but further characterized in that the compound is a sodium salt of an aliphatic disulfonic acid having from 16 to 22 carbon atoms.

12. A process of softening cellulosic fiber paper prod i ucts which comprises applying to said products an aqueous solution of a substance selected from the class consisting of aliphatic disulfonic acids having at least 10 carbon atoms, halogen-containing aliphatic disulfonic acids having at least 10 carbon atoms and containing up to 2 halogen atoms which are attached to a carbon atom of said acid and water-soluble salts of said compounds, said substance being applied to said product in an amount sufficient to soften the surface of said product, and allowing said paper product to dry. 13. A process of softeningcellulosic fiber paper products which comprises spraying on said products an aqueous solution of at least 25% by weight of an alkali metal salt of an aliphatic disulfonic acid having from 10 to 30 carbon atoms, said solution being sprayed in an amount suflicient to deposit from 0.05 to 2% by weight of said salt, based on the dry paper product, and allowing said paper product to dry.

14. A process as in claim 13, but further characterized in that said paper products are selected from the class consisting of sanitary tissues, facial tissues, toilet tissues and paper toweling.

15. A process as in claim 14, but further characterized in that said alkali metal salt is a sodium salt.

16. A process of softening cellulosic fiber paper facial tissue which comprises spraying on said tissue an aqueous solution ofat least 25% by weight of a sodium salt of an aliphatic disulfonic acid having from 16 to 22 carbon atoms, said solution being sprayed on the outer surin that said salt is the disodium salt.

19. A process of producing soft cellulosic fiber paper products which comprises adding a substance selected from the class consisting of aliphatic disulfonic acids having at least 10 carbon atoms, halogenated derivatives of said acids containing up to 2 halogen atoms which are attached to a carbon atom of said acid and water-soluble salts of said compounds to an aqueous slurry of paper pulp, forming the paper pulp into a paper product and thereafter drying said paper product, said substance being present in an amount suflicient to soften the surface of the paper product prepared from said paper pulp. I

References Cited in the file of this patent UNITED STATES PATENTS 1,986,291 Schur Jan. 1, 1935 2,032,645 Youtz Mar. 3, 1936 2,061,619 Downing Nov. 24, 1936 2,412,909 Potter Dec. 17, 1946 FOREIGN PATENTS 280,262 Great Britain Nov. 15, 1927 534,618 Great Britain Mar. 12, 1941 

1. A CELLULOSIC FIBER PAPER PRODUCT COMPRISING A SUBSTANCE SELECTED FROM THE CLASS CONSISTING OF ALIPHATIC DISULFONIC ACIDS HAVING AT LEAST 10 CARBON ATOMS, HALOGENCONTAINING ALIPHATIC DISULFONIC ACIDS HAVING AT LEAST 10 CARBON ATOMS AND CONTAINING UP TO 2 HALOGEN ATOMS WHICH ARE ATTACHED TO A CARBON ATOM OF SAID ACID AND WATERSOLUBLE SALTS OF SAID COMPOUNDS, SAID SUBSTANCE BEING PRESENT IN AN AMOUNT SUFFICIENT TO SOFTEN THE SURFACE OF SAID PAPER PRODUCT. 